This invention relates to an AC generator comprising a rotor which is provided with a pair of iron cores for magnetic, poles including a plurality of magnetic pole teeth. specifically, the invention relates to reducing the weight of the iron cores of the magnetic poles.
FIG. 3 is a sectional view of a conventional AC generator for a vehicle. In FIG. 3, a stator 1 consists of a stator iron core 2 and a stator coil 3. A rotor 4 consists of magnetic pole iron cores 5 and 6 which each have a different polarity and include magnetic pole teeth 5a and 6a which are alternately disposed along a circumference of the iron cores 5 and 6 an exciting coil 7 to be held between the magnetic pole iron cores 5 and 6; axis 8 fixing the magnetic pole iron cores 5 and 6; a pair of slip rings 9 fixed to the rotor axis 8 through an insulating sleeve; and fans 10 and 11 fixed on the magnetic pole iron core 5 and 6. The stator iron core 2 is held between a front bracket 12 and a rear bracket 13 by a binding bolt 14. On the front bracket 12, a plurality of an inlet holes 12a and a plurality of an outlet holes 12b are provided. And on the rear bracket 13, a plurality of an inlet holes 13a and a plurality of an outlet holes 13b are provided for ventilation. The rotor axis 8 is supported on the front bracket 12 and the rear bracket 13 by bearings 15 and 16. A rectifier 18 rectifies an alternating current to a direct current, in which the alternating current is due to an alternating voltage to be induced in the stator coil 3. A voltage adjustor 19 controls an exciting current according to a detected generator voltage so as to adjust a terminal voltage to a predetermined value. A brush holder 20 keeps a brush 21 into contact with the slip ring 9. A protecting cover 22 which is provided with inlet holes 22a covers the rectifier 18 and the voltage adjustor 19. The above described generator allows a magnetic flux .PHI. to pass through the magnetic pole iron cores 5 and 6.
FIG. 4 is a drawing which explains a magnetic circuit of the stator cores and magnetic pole iron cores 5 and 6 of the generator shown in FIG. 3. The stator coils 3 are inserted in each slot of the stator iron core 2 and connected with one another by three phase system. Teeth portions 2a are provided on the stator iron core 2. The magnetic pole teeth portions 5a and 6a of the magnetic pole iron cores 5 and 6 are alternately disposed on the circumference position and are faced to align the teeth portions 2a of the stator iron core 2, where with a space exists between the magnetic pole teeth 5a and 6a, and the teeth portions 2a of the stator iron core 2. When the exciting current is supplied to the exciting coil 7 through the brush holder 20 and the slip ring 9, the magnetic teeth 5a are magnetized to an N pole and the magnetic teeth 6a are magnetized to an S pole so as to form a magnetic circuit with the stator iron core 2 by means of the magnetic flux .PHI..
When the rotor 4 is rotated, the alternating electromotive force is generated in the stator coil 3. The alternating current due to the electromotive force is rectified to the direct current by the rectifier 18. The output voltage corresponding to the rectified current is adjusted to a predetermined value by the voltage adjustor 19.
FIG. 5(a) is a side view of the magnetic pole iron core 5 viewed along the axial direction from the outside of the core 5. The magnetic flux .PHI., along an axial direction of a boss 5a, passes through a radial direction in one end of the iron core 5 and through each magnetic pole tooth 5a in the radial direction. The magnetic flux .PHI. passing through each magnetic pole tooth 5a comes into the corresponding teeth 2a of the stator iron core 2 positioned adjacent to the magnetic pole teeth 5a. FIG. 5(b) is a side view of the other magnetic pole iron core 6 viewed along the axial direction from the inside of the core 6. The magnetic flux .PHI. coming out of the iron core 2 comes into each of the magnetic teeth 6a by passing through the above described space and through a radial direction in one end side of the iron core 6. The magnetic flux .PHI. also moves and along an axial direction of a boss 6b, whereupon that, the magnetic flux .PHI. comes into the boss 5b as shown in FIG. 5(a), which is adjacent to the boss 6b.
On the iron cores 5 and 6 of the above described conventional AC generator, trough portions 5c are provided between the respective magnetic teeth 5a and 6a to have a U shape as shown in FIG. 5(a) and 6(b).
Recently, it has become important to reduce the weight of the AC generator.